The present invention relates to a laser processing apparatus such as a laser drilling machine and a laser cutting machine, and more particularly to a laser processing apparatus having a more processing speed.
In a electronic component processing and metal plate processing, laser processing such as drilling, cutting and marking is widely practiced. For example, in an electronic component processing, a laser forms an inner via hole (IVH) in an inter-layered connection circuit for a multi-layered printed circuit board (PCB). The laser processing apparatus for the PCB controls the position of a laser light or the PCB and forms holes at specified positions on the PCB.
Recently, as the electronic devices are getting smaller and lighter, high density mounting of electronic components on the multi-playered PCB is accordingly required. As a result, the number of IVHs formed in the multi-layered PCB increases, and a forming-hole speed of the laser processing apparatus for the PCB must further increases to comply accordingly with this increase.
FIG. 12 shows a structure of a conventional laser processing apparatus for a PCB. The apparatus comprises the following components: A laser generator 16 for outputting laser light; A galvano device 15 having a two-axis motor and a mirror mounted on the motor, for positioning the laser light by driving two mirrors reflecting the laser light; A condenser lens 19 for condensing the laser light; a work table 17 for positioning a mounted PCB 20 to be processed by the laser light; And a control unit 14 for controlling the laser generator 16, galvano device 15, work table 17, and the entire processing apparatus.
The control unit 14 includes a laser controller 7 for controlling the laser generator 16, a galvano controller 9 for controlling the galvano device 15, a work table controller 5 for controlling the work table 17, and a main controller 4 for controlling these controllers and for analyzing programs and processing conditions. When a PCB 20 is put on the work table 17, the work table controller 5 controls the position of the processing table 17 so that the processing position of the PCB 20 may be located beneath the condenser lens 19. When the work table 17 is positioned at a specified position, the galvano controller 9 controls the position of the galvano device 15 so that the laser light may be emitted to the specified position of the PCB 20. By this position control, the galvano device 15 drives the two-axis motor and positions the two mirrors at appropriate angles individually. After a waiting time for settling in which the galvano device 15 finishes the positioning, the laser controller 7 sends a laser output command to the laser generator 16 according to the processing conditions (laser pulse width, laser peak value, number of laser pulses, laser frequency, and so on). According to the laser output command, the laser generator 16 generates a laser light 18. The laser light 18 is reflected by two mirrors of the galvano device 15, passes through the condenser lens 19, and is emitted to the PCB 20. A hole is formed at the irradiation point of the laser light 18 on the PCB 20. When the laser output is over, in order to drill a next hole, the positions of the galvano device 15 and work table 17 are controlled again. In this manner, holes are formed by the laser light 18 at desired positions on the PCB 20. The galvano controller 9 controls the position of the galvano device 15 by a predetermined, fixed control method according to an acceleration/deceleration constant, and settling time.
With the fixed control method, acceleration/deceleration constants, and settling time, however, the performance of the galvano device 15 may not be sufficiently exhibited depending on a moving distance. For example, being controlled by a step speed command (no acceleration or deceleration time, at a constant speed), the galvano device 15 may respond to the command after delay due to electrical or mechanical delay. When a high speed command is given for a short moving distance, the motor cannot follow the command completely due to the response delay, or do not exceed the limit acceleration of the galvano device 15. Therefore, a vibration does not occur in the galvano device 15. However, when the moving distance is long, the command lasts longer than the response delay, and the galvano device 15 may exceed the limit acceleration and attempt to follow up the high speed command, thereby causing vibration. Therefore, in the control method of using a fixed speed command regardless of the moving distance, the speed command is limited according to the moving distance. The limited speed command is a lower than the capacity of the apparatus when the moving distance is short, and, as a result, the moving time becomes longer for a shorter moving distance.
Increasing a hole density in relation to the recent higher density tends to shorten the hole position interval. The moving distance of the galvano device becomes shorter accordingly, and an increase of a speed in a short moving distance is accordingly demanded. The conventional control method is not enough to induce a speed performance of the galvano device sufficiently for a short moving distance.
A laser processing apparatus comprises a laser generator for producing laser light, a laser controller for controlling the laser generator, a positioning unit (a galvano scanner) for positioning the laser light, a control method memory for storing the control method optimum to the moving distance of the positioning unit, an acceleration/deceleration constant memory for storing the acceleration/deceleration constant corresponding to the moving distance of the positioning unit, a waiting-for-settling time memory for storing the waiting time for settling corresponding to the moving distance of the positioning unit, and a position controller (a galvano controller) for controlling the positioning unit. The position controller controlling the position with using the optimum control method, acceleration/deceleration constant and waiting time for settling makes the processing apparatus operate at high speed.